Flanged connections are used in a variety of industries and applications. For example, flanged connections may be used to operatively connect adjacent sections of pipes, pipelines, or other various fluid carrying or containing structures, including (but not limited to) valves, metering equipment, test equipment, vessels, and the like. In some applications, the fluid carrying or containing structures, and thus the flanged connections, must withstand high fluid pressures. Typically, flanged connections utilize some form of sealing member (e.g., metallic, non-metallic, elastomeric, or composite seals) between two adjacent flange faces to operatively seal flanged connections. Moreover, it may be desirable, or even required by regulations, for flanged connections to be tested, and certified, for specific high pressure applications.
As an example of flanged connections that may require testing or certification, a wellhead is a component of a well, such as an oil or gas well, that provides structural and pressure-containing interfaces at the surface of the well, such as for drilling and production equipment. Accordingly, with reference to the example wellhead of FIG. 1, a wellhead may include various valves, fittings, chokes, tubing, casings, etc. The assembly above the well casings is often referred to as a Christmas tree and includes various fittings for attachment to downstream components during production of a well.
Typically, Christmas tree fittings utilize a so-called ring type joint, or RTJ, which may include a metallic, or other, seal that is operatively seated within a hexagonal channel defined between an outlet flange of a fitting and a flange of a downstream structure that is coupled to the outlet flange. Other types of joints include GRAYLOC™ type joints and joints that utilize lens ring gaskets. Such joints typically require significant labor to seal, including imparting high torques to numerous fasteners to operatively seat the seal and prepare it for testing under fluid high pressure.
Prior to being used in the field, a Christmas tree must be tested to ensure that it can withstand the pressures associated with extraction of high pressure fluid (e.g., oil or gas). Historically, to test a Christmas tree, and thereby certify it for field use, the various outlets of the Christmas tree are capped with a blind flange, such as illustrated in the example of FIG. 2. The retaining fasteners for such a blind flange must be torqued to a Christmas tree outlet to operatively seat the seal and to achieve a clamping force required to oppose the high pressure of the testing fluid. When a Christmas tree has numerous outlets, the procedure of capping all outlets is very time consuming. Upon capping all of the outlets, the Christmas tree is then pressurized with a non-compressible liquid (e.g., water, ethylene glycol, oil, or hydraulic fluid), for example, in the range of 2,500-30,000 psi. Upon being pressurized, the Christmas tree is examined for leaks using testing equipment.
While the above discussion and FIGS. 1 and 2 relate to wellheads and Christmas trees, such as used for oil and gas wells, the test flange assemblies and related methods disclosed herein are not limited to such applications.